Electromagnetic unit for acoustic instruments



- Nov. 3, 1931. w. HASSEL 1,830,433

ELECTROMAGNETIC UNIT FOR ACOUSTIC INSTRUMENTS F'ild Feb. 27 1931 ml l Ill I" H 1 M; 5 III llllll I IN VE IV TOR ATTORNE Y5."

: such as sound reproducers has outer and in- Patented Nov. 3, 193]UNITED STATES WILHELM BASS EL, OF FBANKFORT-OIWTHE MAIN GERMANY,

ASSIGNOR 'ro JOSE]? BUPPERT, OF FRANKFORT-ON-THE-MAIN, GERMANYELECTROMAGKETIC UNIT FOR AGO-U INSTRUMIEN'TQ Application m February 27;1931, Serial No. 518,804, and m Germany February 16, 930.

This invention relates to acoustic instruments and particularly to soundreproducers such as loud speaking telephones and has special referenceto driving units for loud speakers employing large diaphragms.

Loud speakers generally do not reproduce the original soun s asfaithfully as is desirable; considerable losses occurring particularlyfor example, in the reproduction of sounds of low frequency. The objectof the invention is to provide a driving unit which will reproduce asuniformly as possible the variousfrequencies of the original sounds,

while particularly Y avoiding losses of the lower frequencies.

Accordmg to theresent invention an electromagnetic unit or acousticinstruments ner magnetic les on both sides of the axis of vibration o 41vibratory armature, the arrangement being such that the outer polesexert on the armature a turning moment which is in opposition to thatexerted by the inner poles wlth the result that the amplitude ovibration of the armature is proportional to the difference between theopposing moments.

Further accordin to the invention an electromagnetic unit or acousticinstruments employing a vlbratory armature has at least four polar facesof common polarity disposed arrange in such a manner that six oppositean equal number of polar faces of opposite polarity. and field mag .etsof substantiall equal intensity ofrmainetization stantiallyequal'mag'netic flux is produced in the halves o a pole shoe whichbridges like poles of the field magnets.

a 1 Preferably according to th invention the vibratory armature ofrthe electromagnetic unit is provided with lateral extensions de-o signed toretain the vibratory armature in ,the'normal position. In accordancewith a further feature of the-invention in an electromagnetic drivingunit a for acoustic instruments emplo 'ng'aI vibratory armature-thepo'sition of t e pole shoes relatively to one another'isideterminedbythe. positions of 7 screws provided to secure themto/thefield magnets;

I taken on the line IV IV of Figure 1. l

Figure 5 is a 'plan viewof-t'he vibratoryarmature. 7 Two permanenthorseshoe magnets 1, 2 of equal intensity of magnetization provide amagnetic field and are arranged. in spaced relation oneabove the-otherwith like poles I adjacent.-v Laminated pole .shoes 3 and 4 bridge likepoles of the permanent magnets so. that equal flux density obtains ineach half of the pole shoes.

The laminated cured to the magnets by screws 3 4 so that the correctspacing between the pole shoes is pole shoes 3 and 4are'seobtained byplacing the holes for thescrews in appropriate positions in the magnets.The lamlnations have portions stamped out of them in order to form polepieces N N N N S1 S S and S In the outer recesses thus formed are coils5 and 6 which carry the currents to be reproduced while the centralrecesses form air gags between the poles 1 N and N and S and .to thedevice are attached to terminals on a The input leads crewed to anglebrackets 8 is a vibratory armature 9.formed with lateral T shapedextensions 10, 11.v The neckportions 10' 11" are of such elasticity thatwhile the -perm.it

free vibration of the armature a axis 12, the armature is normallyretained in' a centralposition' in the air gap between the =polesspiecesN N N N 0p0SltQly.d1S- posed respectively to pole pieces To one end ofthe armature-is attached and 13 secured to an adjustable 'springy,strip14 which carries a pin 15. 1A conical sound radi- .ating diaphrathe ,pin 15 to w ich it is attached. v

', notshown, is actuated Before describing the operationof the ut" thevin the normal position the vibratory armature is in a mechanically andmagnetically balanced condition. There is no mechanical stress on thearmature due to magnetic forces when there is no current flowing in thecoils 9 as indicated in Figure 4 of the drawings.

5 and 6 and as the flux variation in operation is confined to the poleshoes, the fi'eld of the permanent magnets is not detrimentally affectedand remains constant. The general 10 efiiciency of the driving unit isthus increased.

In operation the varying-currents are applied to the terminals of thedevice so that their direction of flow causes the production ofmagneticpoles m 8 n 8 in the armature The pole n will be repelled by the pole l1 and will be attracted to pole 5,, while 8 will be attracted to N andrepelled by S The pole a will be repelled by N and attr'acted to S,while the pole 8 will be repelled by S and attracted to N The outerpoles N N and S S exert a greater turning moment on the armature 9 aboutits axis 12 than the opposing turning moment exerted'by the inner polesN N and S S Theefiective movement of-the armature about its axis is ofcourse the diiierence between the opposing turning moments.

It is found that a more uniform output 9 and less distortion ofthe lowerfrequencies is obtained with a driving unit constructed in accordancewith the present invention. The opposing turning moment exerted b theinner poles on the armature serves to amp the vibrations at the ends ofthe armature resulting in a :uniform' reproduction of low frequencysounds.

' 1 I claim: g

. 1; An electromagnetic driving unitfor 40 acoustic instrumentscomprising a field mag net, a vlbratory armature, an input winding formagnetizing said armature and outer and inner polar extensions of saidfield magnet located on both sides of the axis of vibration of saidarmature, said outer polar extensions exerting on said armature aturning moment which opposes'the turning moment exerted on said armaturedue to the inner polar extensions such that the result ant amplitude ofvibration of said armature is proportional to the difierence between thesaid opposing moments;

.2. .An electromagnet driving unit for acoustic instruments comprising afield magnet, a vibratory armature, an input windm -for magnetizing saidarmature and outer inner polar extensions of said field magnet of likepolarity on. each side of the axis of vibrationof said armature, saidouter. inner polar extensions being disposed site co-operating polarextensions of oppo- "site polarity. I x f 3. An electromagnetic unit foracoustic instruments comprising afield magnet,-a vibratoryaninputwinding for magnetizing said armature outer and inner polar extensionsof said field magnet on both sides of the axis of vibration of saidarmature, said outer polar extensions .exert ing on said armature aturning moment which opposes the turning moment exerted on said armaturedue to said inner polar extensions and said vibratory armature havinglateral extensions tending to retain it in the normal position.

4. An electromagnetic driving unit for acoustic instruments comprising afield magnet, a system of pole pieces for distributing the field fromsaid field magnet, a vibratory armature and an input winding formagnetizin said armature said systemof pole pieces being readilydetachable from said field magnet and comprising outer and inner polarextensions on both sides of the axis of vibra- .having like. polesopposite each face of the armature, said armature when energized by saidwinding being subjected to opposing turning moments from said outer andinner polar extensions respectively.

6. A11 electro-magnetic driving unit for acoustic instruments comprisinga field magnet, pole pieces connected to the poles of said magnets and-provided with at least four polar extensions of like polarity andsubstantially equal magnetic intensity, a vibratory armature interposedbetween said pole pieces and pivoted to vibrate about an axis midway ofits length, two of said polar extensions being farther from said axisthan another two, and a divided input winding for magnetizing saidarmature in such a manner that the amplitude of vibration of thearmature is proportional to'the difference between 1 the turning momentsthereby created between said armature and the outer and inner polarextension.

7. An electro-magnetic driving umt for acoustic instruments comprising aplurality 1 of field magnets, a pair of pole pieces eac sh like poles ofsaid magnets and each with four polar extensions of substanti y equalmagnetic intensity, a-centrally' j between pivoted vibratory armature'dsaid pole pi and an input winding for magnetizingsai armature.

8, An electromagnetic uni hr acoustic instruments comprising afieldmgnet, a system of pole pieces including pairs of polar extensions fordistributing the field from said magnet, a vibratory armature and aninput windingfor magnetizing said armature, said armature havingresilientvlateral extensions secured at their ends to said magnet forretaining said armature in the normal central position.

9. An electro-magnetic driving unit for acoustic instruments comprisinga field magnet,a system of olepieces including at least four pairs of poar extensions for distributing the field from said magnet, a vibratoryarmature, an input winding mechanically supported on said pole piecesfor magnetiz-' ing said armature, said armature having resilient lateralextensions and means for securing said extensions to said pole piecesystem so that said pole pieces, said armature and said input windingconstitute a unit which is readily detachable from saidfield magnet.

10. An electro-magnetic driving unit for acoustic instruments comprisinga field magnet, a centrally pivoted vibratory armature, a systemincluding pole pieces having at least fourpairs of polar extensions, twoof said pairs being located at each siderof the armature pivot and atdifferent distances therefrom, one polar extension vof each pair beinglocated atone face of the armature and the other polar extension of eachpair being located at the other face of thearmature, all

- said polar extensions at each face of the armature being of likepolarity for distributing the field from said field magnet, and an inputwinding for magnetizing said armature, said winding being divided toform two coils located one on each side of the axis of vibration of saidarmature.

In witness whereof I hereunto subscribe my name this 10th day ofFebruary1931.

WILHELM HASSEL.

